Controlling hydrocarbon injection for filter regeneration

ABSTRACT

A method for providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter within an exhaust system of a diesel engine is provided. The diesel engine comprises an electronic control module, at least one cylinder, and at least one fuel injector in fluid communication with the at least one cylinder, and a diesel oxidation catalyst within the exhaust system. Temperature of a diesel oxidation catalyst output is monitored with an electronic control module. A total amount of hydrocarbons required for diesel particulate filter regeneration is calculated based upon the monitoring of the temperature of the diesel oxidation catalyst output. The total amount of hydrocarbons is injected into an exhaust system upstream of a diesel oxidation catalyst and at least one cylinder with a fuel injector as a post injection.

TECHNICAL FIELD

The present disclosure relates to regeneration of diesel particulate filters, and more particularly to a system and method for regenerating a diesel particulate filter using a system that delivers hydrocarbons used during regeneration of the diesel particulate filter to either, or both, an engine cylinder as an in-cylinder post injection, or as an injection within the exhaust system upstream of a diesel oxidation catalyst and the diesel particulate filter.

BACKGROUND

Many factors, including environmental responsibility efforts and modern environmental regulations on engine exhaust emissions, have reduced the allowable acceptable levels of certain pollutants that enter the atmosphere following the combustion of fossil fuels. Increasingly, more stringent emission standards may require greater control over either or both the combustion of fuel and post combustion treatment of the exhaust. For example, the allowable levels of nitrogen oxides (NOx) and particulate matter have been greatly reduced over the last several years. To address, among other issues, environmental concerns, many diesel engines now have a diesel oxidation catalyst (DOC) as well as a diesel particulate filter (DPF) within an exhaust system of the diesel engine purposed to reduce the amount of NOx and particulate matter released into the atmosphere.

In some diesel engine operating conditions it may be beneficial to provide hydrocarbons, typically in the form of diesel fuel, directly to the exhaust system of the engine at a location upstream of the DOC such that the hydrocarbons will react with the DOC to produce heat and raise temperatures within the DPF to a point sufficient to allow regeneration of the DPF. Injecting hydrocarbons directly into the exhaust system better utilizes the hydrocarbons, therefore, fewer hydrocarbons are required for DPF regeneration. In other diesel engine operating conditions, it may be beneficial to provide hydrocarbons in the form of an in-cylinder post injection such that the hydrocarbons can react with the DOC to produce heat to allow regeneration of the DPF to occur. An example of an engine operating condition where in-cylinder post injection may be utilized include a low exhaust gas flow with low exhaust gas temperatures, as in those conditions hydrocarbons injected directly into the exhaust system may not mix sufficiently to allow the hydrocarbons to react with the DOC to produce heat, and the hydrocarbons may slip through the DOC and enter the DPF. One drawback of utilizing in-cylinder post injection is that some fuel does not ever enter the exhaust system, but may flow past piston rings and into a lubrication oil system of the engine, diluting the oil and potentially damaging engine components. However, in still other diesel engine operating conditions it may be beneficial to provide hydrocarbons both directly into the exhaust system and via in-cylinder post injection. Some engines are equipped to provide hydrocarbons both directly to the exhaust system, and via in-cylinder post injection, but these existing systems utilize separate control systems for each of the in-cylinder post injection and injections directly into the exhaust system, but these existing systems do not allow simultaneous hydrocarbon injection into both the exhaust system and in-cylinder post injection.

Therefore, a need exists for a system and method of providing hydrocarbons to be used to raise exhaust temperatures that allow regeneration of a DPF to occur that allows delivery of hydrocarbons via an in-cylinder post injection, an injection directly into an exhaust system upstream of a DOC, or a combination of both in-cylinder post injection and directly into the exhaust system upstream of a DOC.

SUMMARY

According to one process, a method of providing hydrocarbons to an engine exhaust to for regenerating a diesel particulate filter within an exhaust system of a diesel engine is provided. The diesel engine comprises an electronic control module, at least one cylinder, and at least one fuel injector in fluid communication with the at least one cylinder, and a diesel oxidation catalyst within the exhaust system. A diesel particulate filter regeneration request is received from an electronic control module. Temperature of a diesel oxidation catalyst output is monitored with the electronic control module. The electronic control module determines a total amount of hydrocarbons required for diesel particulate filter regeneration. A first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an injection directly into an exhaust system upstream of a diesel oxidation catalyst is determined with the electronic control module. A second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an in-cylinder post injection is determined with the electronic control module. The first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration is injected into the exhaust system upstream of the diesel oxidation catalyst based upon an output of the electronic control module. The second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an in-cylinder post injection is injected based upon an output of the electronic control module.

According to another process, a method for providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter within an exhaust system of a diesel engine is provided. The diesel engine comprises an electronic control module, at least one cylinder, and at least one fuel injector in fluid communication with the at least one cylinder, and a diesel oxidation catalyst within the exhaust system. Temperature of a diesel oxidation catalyst output is monitored with an electronic control module. A total amount of hydrocarbons required for diesel particulate filter regeneration is calculated based upon the monitoring of the temperature of the diesel oxidation catalyst output. The total amount of hydrocarbons is injected into an exhaust system upstream of a diesel oxidation catalyst and at least one cylinder with a fuel injector as a post injection.

According to one embodiment, a hydrocarbon injection system for an internal combustion engine having an exhaust system with a diesel particulate filter and a diesel oxidation catalyst, the hydrocarbon injection system comprises an electronic control module, an engine speed sensor, an exhaust system, and at least one in-cylinder fuel injector. The electronic control module has a memory and a processor. The engine speed sensor is disposed in communication with the electronic control module. The engine torque output estimator is disposed in communication with the electronic control module. The exhaust system has a diesel oxidation catalyst, a diesel oxidation catalyst temperature sensor is disposed adjacent the diesel oxidation catalyst and is disposed in communication with the electronic control module, a diesel particulate filter is disposed downstream of the diesel oxidation catalyst, and an exhaust system hydrocarbon injector is disposed upstream of the diesel oxidation catalyst and is disposed in communication with the electronic control module. The at least one in-cylinder engine fuel injector is disposed within a cylinder of the engine, the fuel injector is disposed in communication with the electronic control module. The electronic control module determines a total amount of hydrocarbons required for diesel particulate filter regeneration based upon a diesel oxidation catalyst output temperature sensor. The electronic control module generates a single hydrocarbon injection output causing at least one of the in-cylinder fuel injector and the exhaust system hydrocarbon injector to inject hydrocarbons when a diesel particulate filter regeneration is required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an engine having an exhaust system with an diesel particulate filter a diesel oxidation catalyst, and a hydrocarbon injector disposed in the exhaust system.

FIG. 2 is a schematic diagram showing an electronic control module and sensors used to determine an amount of hydrocarbons required for a diesel particulate filter regeneration, and where the hydrocarbons should be delivered.

FIG. 3 is a schematic diagram showing one method of providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter.

FIG. 4 is a schematic diagram showing another method of providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter.

DETAILED DESCRIPTION

FIG. 1 shows an engine 10 having an exhaust system 12. The exhaust system 12 comprises a diesel oxidation catalyst (DOC) 14, a DOC temperature sensor 16, a diesel particulate filter (DPF) 18, and an exhaust system hydrocarbon injector 20. The engine 10 additionally has an electronic control module (ECM) 22, sometimes referred to as an engine control module, or an engine control unit. The ECM 22 control operations of many aspects of the engine 10, such as fuel injection, emissions based engine settings, combustion based engine settings, and DPF regeneration, to name a few. The DOC temperature sensor 16 is in communication with the ECM 22.

The engine 10 additionally has a plurality of cylinders 24, each of which has a fuel injector 26. The fuel injector 26 are capable of performing multiple injection of fuel per cylinder for each combustion cycle, such as a pre-injection, a main injection, and a post-injection, where the main injection is the fuel injection to provide the required power output of the engine 10, while the pre-injection occurs before the main injection, and the post-injection occurs after the main injection.

The engine 10 additionally has an engine speed sensor 28 that is also in communication with the ECM 22 and is used to determine the speed that the engine is running

As shown in FIG. 1, the DOC 14 is located upstream of the both the DOC temperature sensor 16 and the DPF 18. The exhaust system hydrocarbon injector 20 is disposed upstream of the DOC 14. The exhaust system hydrocarbon injector 20 injects hydrocarbons, such as diesel fuel, into the exhaust system 12 in order to raise the temperature of the DOC 14, as well as exhaust within the exhaust system 12. The DPF may undergo regeneration when the temperature within the exhaust system 12 is above a certain level.

Turning now to FIG. 2, a portion of an electronic control system of the engine 10 is schematically depicted. The ECM 22 has a processor 30 and a memory 32. The ECM 22 receives inputs from a variety of sensors or controlled parameters such as output of the engine speed sensor 32, the DOC temperature sensor 36, an engine torque estimate 38 and intake air flow 40. The processor 30 may utilize the inputs to retrieve an output from a look up table stored in the memory 32, or may utilize the inputs to calculate an intermediate result that is compared with data stored in the memory 32 to generate output signals related to DPF regeneration.

For instance, the processor 30 of the ECM 22 generates a total amount of hydrocarbons that are required for regeneration of the DPF 18. The total amount of hydrocarbons required for regeneration of the DPF 18 is driven by the input from the DOC temperature sensor 36. It is contemplated that the total amount of hydrocarbons required for regeneration of the DPF 18 may be stored in a lookup table in the memory 32, or may be calculated utilizing an algorithm stored in the memory 32 of the ECM 22.

Additionally, a percentage 44 of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the exhaust system hydrocarbon injector 18 may be stored in a lookup table in the memory 32, or may be calculated utilizing an algorithm stored in the memory 32 of the ECM 22. The percentage 44 of the total hydrocarbons percentage of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the exhaust system hydrocarbon injector 18 will vary based on engine operating factors such as engine speed input 34, engine torque estimate 38, and input on intake air flow 40.

Similarly, a percentage 46 of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the fuel injectors 26 as an in-cylinder post injection may be stored in a lookup table in the memory 32, or may be calculated utilizing an algorithm stored in the memory 32 of the ECM 22. The percentage 46 of the total hydrocarbons percentage of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the fuel injectors 26 as an in-cylinder post injection will vary based on engine operating factors such as engine speed input 34, engine torque estimate 38, and input on intake air flow 40.

While shown in FIG. 2 as being calculated by the ECM 22, it is contemplated according to other alternative embodiments that the total amount of hydrocarbons required for DPF regeneration 42 would be communicated to a sub-processor that calculates the percentage 44 of the total hydrocarbons percentage of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the exhaust system hydrocarbon injector 18, and the percentage 46 of the total hydrocarbons percentage of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the fuel injectors 26 as an in-cylinder post injection.

It is also contemplated that the percentage 44 of the total hydrocarbons percentage of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the exhaust system hydrocarbon injector 18 will be set to zero if a regeneration occurs in an engine of a vehicle that is stationary.

It is additionally contemplated that filtering may be utilized to control the transition of changes in the percentage 44 of the total hydrocarbons percentage of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the exhaust system hydrocarbon injector 18 and the percentage 46 of the total hydrocarbons percentage of the total hydrocarbons required for DPF regeneration that will be injected into the exhaust system 12 by the fuel injectors 26 as an in-cylinder post injection. Filtering is utilized such that a transient change in one of the inputs 34, 36, 38, 40 of the ECM 22 does not cause a sudden change in the percentages 44, 46, but that a sustained change to one of the inputs may change the percentages 44, 46. The filtering may be a dual hysteresis type of filtering such that a transition from not injecting hydrocarbons into the exhaust system 12 using the hydrocarbon injector 18 is initiated only after a certain first threshold is exceeded and that a transition to 100% of the hydrocarbons will be injected into the exhaust system 12 using the hydrocarbon injector 18 only after a second threshold is exceeded. Similarly, a transition from 100% of the hydrocarbons being injected into the exhaust system 12 using the hydrocarbon injector 18 will occur only after a third threshold is not exceeded, and a transition to 0% of the hydrocarbons being injected into the exhaust system 12 using the hydrocarbon injector 18 will occur only after a fourth threshold is not exceeded. Thus, sudden changes in the percentage of the hydrocarbons delivered to the exhaust system 12 by the hydrocarbon injector 18 caused by transient engine operations is avoided by filtering. Similarly, time dealy filtering may also be utilized, such that operating conditions must show that a change in hydrocarbon delivery to the exhaust system 12 is required for a predetermined period of time before any modification to hydrocarbon delivery is made.

It is additionally contemplated that filter may be utilized to provide smooth transitions in amounts of hydrocarbons delivered from the hydrocarbon injector 18 and the fuel injectors 26. Such filtering avoids abrupt transitions and provides more gradual changes the amount of hydrocarbons that are delivered to the exhaust system 12 by the hydrocarbon injector 18 and the fuel injectors 26 when a transition in the amount of hydrocarbons provided by the hydrocarbon injector 18 is required.

FIG. 3 shows one method 50 of providing hydrocarbons to an engine exhaust for regenerating a DPF. The method 50 receives a DPF regeneration request, such as from a user, or generates a DPF regeneration request as shown at block 52. Next, the method 50 monitors the temperature of the DOC with the ECM at block 54.

A total amount of hydrocarbons required for DPF regeneration is determined at block 56. A first percentage of the total amount of the hydrocarbons required for DPF regeneration for delivery directly into the exhaust system is determined at block 58. Similarly, a second percentage of the total amount of the hydrocarbons required for DPF regeneration for delivery as an in-cylinder post injection is determined at block 60. As mentioned above, the total amount of hydrocarbons required for regeneration, as well as the first percentage and the second percentage may be contained in a lookup table in the memory 32 of the ECM 22, or may be calculated using the processor 30 of the ECM 22.

The first percentage of the total amount of the hydrocarbons required for DPF regeneration is injected directly into the exhaust system at block 62. The second percentage of the total amount of the hydrocarbons required for DPF regeneration is injected as an in-cylinder post injection at block 64. It is contemplated that the injections of hydrocarbons 62, 64 may occur generally simultaneously, or that the in-cylinder post injection 64 may occur slightly before the direct injection into the exhaust system 62.

FIG. 4 shows another method 70 of providing hydrocarbons to an engine exhaust for regenerating a DPF. The method 70 monitors the temperature of the DOC with the ECM at block 72. A total amount of hydrocarbons required for DPF regeneration is determined at block 74. The total amount of the hydrocarbons required for DPF regeneration is injected directly into the exhaust system and as an in-cylinder post-injection at block 76. It is contemplated that the injection directly into the exhaust system and the in-cylinder post injection will be occurring simultaneously in at least some operating conditions.

It will be understood that a control system may be implemented in hardware to effectuate the method. The control system can be implemented with any or a combination of the following technologies, which are each well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc.

When the control system is implemented in software, it should be noted that the control system can be stored on any computer readable medium for use by or in connection with any computer related system or method. In the context of this document, a “computer-readable medium” can be any medium that can store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM) (electronic), a read-only memory (ROM) (electronic), an erasable programmable read-only memory (EPROM, EEPROM, or Flash memory) (electronic), an optical fiber (optical) and a portable compact disc read-only memory (CDROM) (optical). The control system can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. 

What is claimed is:
 1. A method of providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter within an exhaust system of a diesel engine, the diesel engine comprising an electronic control module, at least one cylinder, and at least one fuel injector in fluid communication with the at least one cylinder, and a diesel oxidation catalyst within the exhaust system, the method comprising: receiving a diesel particulate filter regeneration request from an electronic control module; monitoring temperature of a diesel oxidation catalyst output with the electronic control module; determining a total amount of hydrocarbons required for diesel particulate filter regeneration with the electronic control module; determining a first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an injection directly into an exhaust system upstream of a diesel oxidation catalyst; determining a second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an in-cylinder post injection with the electronic control module; injecting the first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration into the exhaust system upstream of the diesel oxidation catalyst; and injecting the second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an in-cylinder post injection based upon an output of the electronic control module.
 2. The method of claim 1, wherein the determining of the total amount of hydrocarbons required for diesel particulate filter regeneration of the engine is based upon inputs from a temperature sensor adjacent the diesel oxidation catalyst.
 3. The method of claim 1, wherein the determining a first percentage of the total amounts of hydrocarbons required for diesel particulate filter regeneration for delivery as an injection directly into an exhaust system is based upon inputs from a engine speed sensor disposed in communication with an electronic control module, an engine torque output estimator of the electronic control module, an input from a temperature sensor adjacent the diesel oxidation catalyst, and an input from an air intake flow sensor.
 4. The method of claim 1, wherein the determining the first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an injection directly into an exhaust system upstream of a diesel oxidation catalyst and the second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration is performed on a single processor.
 5. The method of claim 1, wherein the determining the first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an injection directly into an exhaust system upstream of a diesel oxidation catalyst will equal zero at an engine idle.
 6. The method of claim 1, wherein the injecting the first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration into the exhaust system upstream of the diesel oxidation catalyst and the second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an in-cylinder post injection occur generally simultaneously.
 7. The method of claim 1, wherein the injecting the first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration into the exhaust system upstream of the diesel oxidation catalyst is initiated following an initiation of injecting the second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration for delivery as an in-cylinder post injection
 8. The method of claim 1, further comprising transitioning an initial first percentage of the total amounts of hydrocarbons required for diesel particulate filter regeneration for delivery as an injection directly into an exhaust system is based upon inputs from a engine speed sensor disposed in communication with an electronic control module, an engine torque output estimator of the electronic control module, an input from a temperature sensor adjacent the diesel oxidation catalyst, and an input from an air intake flow sensor to a modified first percentage of the total amounts of hydrocarbons required for diesel particulate filter regeneration based upon changes in the inputs from the engine speed sensor, the engine torque output estimator, the temperature sensor adjacent the diesel oxidation catalyst, and the air intake flow sensor.
 9. The method of claim 8, wherein the transitioning from the initial first percentage of the total amounts of hydrocarbons required for diesel particulate filter regeneration to the modified of the total amounts of hydrocarbons required for diesel particulate filter regeneration is a filtered transition requiring changes in the inputs from the engine speed sensor, the engine torque output estimator, the temperature sensor adjacent the diesel oxidation catalyst, and the air intake flow sensor to exceed a predetermined amount for any transitioning to occur.
 10. A method for providing hydrocarbons to an engine exhaust for regenerating a diesel particulate filter within an exhaust system of a diesel engine, the diesel engine comprising an electronic control module, at least one cylinder, and at least one fuel injector in fluid communication with the at least one cylinder, and a diesel oxidation catalyst within the exhaust system, the method comprising: monitoring temperature of a diesel oxidation catalyst output with an electronic control module; calculating a total amount of hydrocarbons required for diesel particulate filter regeneration based upon the monitoring of the temperature of the diesel oxidation catalyst output; and injecting the total amount of hydrocarbons into an exhaust system upstream of a diesel oxidation catalyst and at least one cylinder with a fuel injector as a post injection.
 11. The method of claim 10, wherein a first percent of the total amount of hydrocarbons are injected into the exhaust system upstream of the diesel oxidation catalyst based upon monitoring engine intake air flow with an electronic control module.
 12. The method of claim 10, wherein a first percent of the total amount of hydrocarbons are injected into the exhaust system upstream of the diesel oxidation catalyst based upon monitoring engine speed with an electronic control module.
 13. The method of claim 10, wherein a first percent of the total amount of hydrocarbons are injected into the exhaust system upstream of the diesel oxidation catalyst based upon monitoring engine torque output with an electronic control module.
 14. The method of claim 10, wherein a first percent of the total amount of hydrocarbons are injected into the exhaust system upstream of the diesel oxidation catalyst, and a second percent of the total amount of hydrocarbons are injected into the at least one cylinder with a fuel injector as a post injection, the first percent and the second percent varying over time based upon changes in engine speed.
 15. The method of claim 14, wherein the first percent and the second percent varying over time require changes in engine speed to exceed a predefined amount.
 16. The method of claim 10, wherein a first percent of the total amount of hydrocarbons are injected into the exhaust system upstream of the diesel oxidation catalyst, and a second percent of the total amount of hydrocarbons are injected into the at least one cylinder with a fuel injector as a post injection, the first percent and the second percent varying over time based upon changes in engine torque output.
 17. A hydrocarbon injection system for an internal combustion engine having an exhaust system with a diesel particulate filter and a diesel oxidation catalyst, the hydrocarbon injection system comprising: an electronic control module having a memory and a processor; an engine speed sensor disposed in communication with the electronic control module; an engine torque output estimator disposed in communication with the electronic control module; an exhaust system having a diesel oxidation catalyst, a diesel oxidation catalyst temperature sensor disposed adjacent the diesel oxidation catalyst and disposed in communication with the electronic control module, a diesel particulate filter disposed downstream of the diesel oxidation catalyst, and a exhaust system hydrocarbon injector disposed upstream of the diesel oxidation catalyst and disposed in communication with the electronic control module; and at least one in-cylinder engine fuel injector disposed within a cylinder of the engine, the fuel injector disposed in communication with the electronic control module; wherein the electronic control module determines a total amount of hydrocarbons required for diesel particulate filter regeneration based upon a diesel oxidation catalyst output temperature sensor, and the electronic control module generates a single hydrocarbon injection output causing at least one of the in-cylinder fuel injector and the exhaust system hydrocarbon injector to inject hydrocarbons when a diesel particulate filter regeneration is required.
 18. The hydrocarbon injection system of claim 17, wherein the electronic control module generates a single hydrocarbon injection output causing both the in-cylinder fuel injector and the exhaust system hydrocarbon injector to inject hydrocarbons when a diesel particulate filter regeneration is required.
 19. The hydrocarbon injection system of claim 18, wherein a first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration is injected with the exhaust system hydrocarbon injector and a second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration is injected with the in-cylinder fuel injector based upon outputs of the engine speed sensor received by the electronic control module.
 20. The hydrocarbon injection system of claim 18, wherein a first percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration is injected with the exhaust system hydrocarbon injector and a second percentage of the total amount of hydrocarbons required for diesel particulate filter regeneration is injected with the in-cylinder fuel injector based upon outputs of the engine torque estimator received by the electronic control module. 